1. Field of the Invention
This invention relates to hypodermic syringes, and more particularly concerns a needle assembly adapted to protect people using hypodermic syringes from accidental needle sticks, and further to render used needles unusable.
2. Description of the Prior Art
Health professionals and others who use hypodermic syringes to inject medicine or other substances into patients or to obtain samples of blood or other bodily fluids from people are subject to risk of infection if they are stuck with a contaminated needle that has been withdrawn from an infected person. This is a matter of special concern when facing the possibility of dealing with patients who have infectious hepatitis or Acquired Immune Deficiency Syndrome (AIDS), but it is preferable to avoid or minimize the possibility of infection with any disease. The needle of a hypodermic syringe, being sharp to penetrate the skin readily for its intended purpose, is a threat to penetrate clothing and rubber gloves of the health professional using the hypodermic syringe and thus to puncture the skin of the health professional. The threat of contamination is present with needles that are used for subcutaneous and intramuscular injection, but it is particularly threatening with needles used for intravenous injection of and for the drawing of blood or other body fluids from veins or other parts of the body. Likewise, hypodermic syringes used in dentistry also pose a threat of accidental contamination.
A hypodermic syringe is herein defined as a combination of a hollow needle or cannula anchored in a hub, and a syringe comprised of a plunger slidingly interactive with a fluid-confining transparent barrel that releasibly engages the hub. If the hypodermic syringe is designed for injection or withdrawal using positive pressure or vacuum produced by the plunger, then the needle normally terminates in the hub. The barrel is typically marked with graduations to measure quantities of fluids injected or withdrawn. If the hypodermic syringe is designed for use in a vacuum withdrawal system or for dental use, then the needle is normally double-ended, passing completely through the hub and extending beyond the hub in both directions. The hypodermic syringe in this case serves as a support for a medication carpule having a soft plastic that is pierced by the needle, thereby enabling the plunger to dispense the contents of the carpule. In either event, the forwardly protruding needle is normally equipped with a removable cover to protect health professionals from accidental contact with the point of the needle.
For any of the uses described above, universal practice is either to discard the needle after one use, or else to sterilize it before another use. During the act of disposal, the contaminated needle is exposed between its site of use and a dispenser device. Carelessness on the part of the health professional or other user of the hypodermic, distractions occasioned by telephone calls and the like, or accidental jostling by passersby, all make it possible to bring the contaminated point of the needle into contact with the body of the health professional. A particular threat exists when the needle cover is replaced before the needle is discarded. In this case the health professional typically holds the needle cover in one hand and inserts the needle into an opening in the cover. The same distracting factors may cause the contaminated point of the needle to come into contact with his or her hand.
The danger described above has been the subject of several patents. Strauss, U.S. Pat. No. 4,664,654, "Automatic Protracting and Locking Hypodermic Needle Guard" is an example of one means for protecting the tip of a contaminated needle. Strauss teaches a spring-activated sliding member that covers the needle. The sliding member can be locked in place to protect the point of the needle from coming in contact with anything. When the sliding member is unlocked, the needle is exposed for use. The sliding member is placed against the skin after the needle is inserted. The spring maintains force on the sliding member, and restores it to the protective position when the needle is withdrawn. The device taught by Strauss has the disadvantage of being relatively complex mechanically, which increases it manufacturing cost, and also of coming in contact with the skin of a patient. In addition, the device taught by Strauss is limited to use for subcutaneous and intramuscular injection or for the drawing of blood samples.
U.S. Pat. No. 4,139,009 to Alvarez discloses a retractable needle cover which is comprised of a hub member and a sliding member joined by a multiplicity of resilient arms to maintain the distance along the needle between the hub and sliding members. The arms are bowable away from the needle and are splayed outward upon retraction of the sliding member to allow penetration of body tissue. However, the splayed arms render the device impractical for usage in dentistry as the splayed arms prohibit use in the tight confines of the oral cavity.
U.S. Pat. Nos. 4,702,738 and 4,801,295 to Spencer discloses an integral system in which the needle, syringe and protective cover are interactive in use. The protective device does not lend itself toward usage with standard syringes and commonly available needles. The device disclosed by Laico in U.S. Pat. No. 4,892,521 utilizes either guide rods or telescopic tubes in order to maintain the locked position of the needle covering device. Such guide means constitute additional moving parts, causing complexity of use and high manufacturing cost.
U.S. Pat. No. 4,863,436 to Glick discloses a hypodermic syringe having a protection device comprising a long hub which slidingly supports a first cylindrical cover. A second cover is employed to lock the first cover in place. The device does not shield both ends of a double-ended needle such as those used in dentistry. The hub effectively increases the length of the hypodermic syringe, thereby causing cumbersome operation. The necessary minipulation of the second cover makes the device difficult to use.
It is therefore an object of the present invention to provide a protective covering device for the cannula needle of a hypodermic syringe.
It is another object of the present invention to provide a needle covering device of the aforesaid nature which is adaptable to a multiplicity of currently available hypodermic syringes.
It is yet another object of the present invention to provide a device of the aforesaid nature which will effectively cover both ends of a double-ended cannula needle when detached from a syringe.
It is still another object of the present invention to provide a needle covering device of the aforesaid nature which has a minimal number of moving parts, is simple to use and amenable to low cost manufacture.